Corrosion inhibited phosphoric acid composition

ABSTRACT

A CORROSION INHIBITED PHOSPHORIC ACID COMPOSITION COMPRISING A PHOSPHORIC ACID SOLUTION HAVING ADDED THERETO AN EFFECTIVE AMOUNT OF THE REACTION PRODUCT OF HYDROGEN IODIED AND AN ORGANIC AMINE HAVING A MOLECULAR WEIGHT BETWEEN ABOUT 50 AND ABOUT 500.

United States Patent 3,585,151 CORROSION INHIBITED PHOSPHORIC ACID COMPOSITION Olen L. Riggs, Jr., Ponca City, Okla., assignor to Continental Oil Company, Ponca City, Okla. Filed Feb. 9, 1968, Ser. No. 704,221 Int. Cl. C23f 11/00 US. Cl. 252--390 4 Claims ABSTRACT OF THE DISCLOSURE A corrosion inhibited phosphoric acid composition comprising a phosphoric acid solution having added thereto an effective amount of the reaction product of hydrogen iodide and an organic amine having a molecular weight between about 50 and about 500.

This invention relates to novel and useful compositions and methods for inhibiting the corrosion of metals by phosphoric acid.

At the present time metals are protected from phosphoric acid corrosion by rubber linings and by the addition of certain inhibitors to the phosphoric acid.

It has nOW been unexpectedly discovered that the corrosivity of metal surfaces in contact with phosphoric acid can be markedly reduced by adding to said acid an effective amount of the material obtained by reacting hydrogen iodide with an organic amine having a molecular weight between about 50 and 500.

The preferred organic amines which can be reacted with hydrogen iodide to produce the desired reaction product are essentially all aliphatic alkyl mono or diamines, imidazolines, guanidines, ethoxylated monoamines and ethoxylated diamines. Some specific examples are shown by the following structural formulas:

NH: $13123: E IQET fiiis to z tlfifi's.

H 3 Rl ICHgCH CH NH R=12 to 16 carbons.

(CHzCHzO);H 4 RI I R=11 to 17 carbons.

(H2CH20)yH N-CH3 5 R- JHQ R=11 to 17 carbons.

N HzCHgNHz (CHzCHzO) H l H2CH2O)xH 6 RILCH CHzCHzN R= to 16 carbons.

(CH2CH20)yH H R-C-CHs 7 HNCHzCHzCHzNHz R=10 to 16 carbons.

Hydrogen iodide is the preferred iodide containing reactant; however, gaseous 1 or alkyl iodides in acidic solution under controlled temperatures can also be used.

The mole ratio of amine to hydrogen iodide can vary from about 1:3 to about 3:1, with the preferred ratio being 1:1.

The concentration of reaction product effective to give the desired results can vary from about 5 to about 500 parts per million with the upper limit being more of an 3,585,151 Patented June' l5, 1971 Ice.

EXAMPLE 1 One mole of an organic amine having the structur formula R-C-CH:

HNCHZ CHZCHQNHQ was Weighed into a three-necked round bottom'flask. One hundred fifty grams of isopropanol and one mole of hydrogen iodide were added. The flask was then heated to C. and allowed to reflux for 3 hours. The entire reaction product was then tested as a corrosion inhibitor for phosphoric acid. The results are shown in Example 2.

EXAMPLE 2 Corrosion tests were made using the reaction product of Example 1. The tests consisted of pouring 300 ml. volumes of 75 percent by weight of H PO into cells containing specimens of annealed 1020 carbon steel. TWO groups of tests were run, one at 55 C. and one at 75 C. The results are given in Table 1 and Table 2.

TABLE 1 75% wt. H PO4-55 C.2 hrS.

R=14 carbons.

Concentration active Percent Corrosion inhibitor, Wt. ss, protecrate, mg Inhibitor sample p.p.m. g. tion cmJ/hr None 0 1. 08240 29. 02 1 5 0. 22445 79. 3 6. 02 2- 20 0. 11245 89. 6 3. 01 3---. 50 0. 11055 89. 8 2. 96 4. 0. 02880 97. 4 0. 77 5- 200 0. 01470 98. 7 0. 39 6. 500 0.0060 99. 7 0. 06 Unreacted amine of Example 1 500 0 31962 69. 1

TABLE 2 75% wt. H3PO4-75 C.2 hrs.

Concentratlon active Percent Corrosion inhibitor, Wt. loss. protecrate, mg./ Inhibitor sample ppm. g. tion cmJ/hr.

Table 3 illustrates that the beneficial effect does not occur when the amines and hydrogen iodide are present as an unreacted simple mixture.

Having thus described the invention by providing specific examples thereof, it is to be understood that no undue limitations or restrictions are to be drawn by reason thereof and that many variations and modifications are within the scope of the invention.

What is claimed is:

1. A corrosion inhibited phosphoric acid composition consisting essentially of said phosphoric acid and from about parts per milion to about 500 parts per million of the material obtained from the reaction between hydrogen iodide and an organic amine having a structural formula selected from the group consisting of:

NH; 1 R-CHz-HCH3 R=4 to 11 carbons. 2 R-NHz R=18 to 22 carbons.

H 3 RI ICH CH C HzNHz R=12 to 16 carbons.

H 4 R( 3CH R= to 16 carbons.

HNCH2CH CH2NHz where R is an alkyl group and with said organic amine having a molecular weight between about 50 and about 500 and wherein said reaction is carried out under reflux conditions at about 80 C. for about 3 hours in the presence of isopropanol and the raito of hydrogen iodide to said organic amine is from about 1:3 to about 3:1.

2. The composition of claim 1 wherein the organic amine has the following structural formula:

1 RC--CH3 H-N-CHz-CHPCHzNH:

where R=10 to 16 carbons.

3. A method of protecting metal surfaces against corrosion caused by phosphoric acid wherein said method consists essentially of adding from about 5 parts per million to about 500 parts per million of the product obtained by the reaction between hydrogen iodide and an organic amine having a structural formula selected from the group consisting of:

References Cited UNITED STATES PATENTS 2,567,156 9/1951 Malowan 252-390X 3,260,673 7/1966 Fisher 252148X 3,371,118 2/1968 Lundeen et a1. 260-583 HERBERT B. GUYNN, Primary Examiner A. I. RODY, Assistant Examiner US. Cl. X.R. 

